1. Field of the Invention
This invention relates to crosslinked elastomers, and processes for making and products made from such elastomers. In one aspect, this invention relates to elastomers crosslinked with a compound other than sulfur or a peroxide while in another aspect, the invention relates to crosslinking functionalized elastomers.
2. Description of the Related Art
Traditionally, elastomers have been crosslinked (also known as vulcanized) using either (i) a free radical curing system initiated by radiation or a peroxide, or (ii) sulfur, but the resulting products have often been unsatisfactory for one or more of several reasons. For example, low molecular weight by-products (which can have detrimental effects on the physical properties of the crosslinked elastomer) are often produced with free radical curing systems, and sulfur-crosslinked elastomers can have odor and color problems as well as less than desirable heat aging stability and weatherability characteristics due to unsaturation in the polymer chain and/or weak sulfur linkages. Alternative crosslinking systems have been proposed, e.g. U.S. Pat. 4,801,647 discloses crosslinking an ethylene-propylene-diene elastomer grafted with maleic anhydride with diamine crosslinking agents, but the development of other elastomer crosslinking systems are still of interest to many end-users of elastomers.
According to this invention, an at least partially crosslinked elastomer comprises the reaction product of (i) an elastomeric polymer containing reactive substituents, and (ii) a crosslinking agent (also known as a vulcanizing agent) (a) containing two or more reactive substituents differing from those contained in the elastomeric polymer, and (b) having a number average molecular weight of less than about 2000, each of the reactive substituents selected such that those of the elastomer will react with those of the crosslinking agent to at least partially crosslink the elastomer, and each of the reactive substituents selected from the group consisting of carboxylic acid, carboxylic anhydride, carboxylic acid salt, carbonyl halide, hydroxy, epoxy, and isocyanate.
In another aspect of this invention, the at least partially crosslinked elastomer is prepared by a process comprising reacting by contacting (i) an elastomeric polymer containing reactive substituents, and (ii) a crosslinking agent (a) containing two or more reactive substituents differing from those contained in the elastomeric polymer, and (b) having a number average molecular weight of less than about 2000, each of the reactive substituents selected such that those of the elastomer will react with those of the crosslinking agent to at least partially crosslink the elastomer and each of the reactive substituents selected from the group consisting of carboxylic acid, carboxylic anhydride, carboxylic acid salt, carbonyl halide, hydroxy, epoxy, and isocyanate.
The present invention also includes articles comprising at least one of the at least partially crosslinked elastomers of this invention, and the shaping of these articles, preferably in a melt processing operation.